New antiphishing, antispam specifications unveiled

The DomainKeys Identified Mail spec helps sort and identify legitimate e-mail

Specifications for a new e-mail authentication tool to help fight against phishing and spam were published yesterday by the Internet Engineering Task Force (IETF), opening the way for software vendors and e-mail service providers to find better ways to protect e-mail recipients.

The specifications were announced for DomainKeys Identified Mail (DKIM), a new technology that combines several existing antiphishing and antispam methods to create an improved way to sort and identify legitimate e-mail. The specifications provide details that independent software vendors and e-mail service providers can use to build the protections into their products and services immediately.

Instead of using a traditional IP address to identify the sender of each message, DKIM adds a digital signature associated with the organization's domain name. That signature is then validated invisibly at the recipient's end. "White lists" and "black lists" are then used by the e-mail infrastructure software to validate the reputation of the sender.

"Domain names are far more stable than IP addresses," said Dave Crocker, an IT consultant and contributor to the DKIM project. "Domain names align with an organization far better than an IP address."

Because it incorporates a digital signature, "it allows a piece of e-mail to be identified definitively as somebody's," rather than as an e-mail coming from an IP address that could used by multiple people or a spam bot," he said. "It's a step along the way to regaining trust in e-mail," Crocker added.

The core technologies used in DKIM have been around for years, he said. "We're taking existing pieces and using them together in new ways."

DomainKeys is a project begun several years ago by Yahoo Inc. as a way to fight phishing and spam; the Identified Internet Mail project was begun by Cisco Systems Inc.

The DomainKeys project was particularly innovative because it specified the use of domain names rather than IP addresses to authenticate senders, Crocker said. DomainKeys also used the existing Domain Name System (DNS) to transmit the public keys needed for encryption, rather than adding yet another infrastructure layer.

An informal consortium of about a dozen IT vendors and organizations, including Yahoo, Cisco, EarthLink Inc., Microsoft Corp., PGP Corp., StrongMail Systems Inc., VeriSign Inc. and Sendmail Inc., have met for a year to create the new specifications for DKIM. It was first submitted to the IETF for consideration as a new e-mail standard to fight phishing and spam in July 2005.

To make it work, DKIM now has to be adopted and incorporated by independent software vendors into their e-mail applications and related infrastructures. Paul Hoffman, a director at the Domain Assurance Council, a trade association for the domain reputation industry, said he believes that e-mail service providers such as Yahoo and Google Inc. will lead the way.

"You're going to see a bunch of adoption from the receivers within the next six months, and that will spur the senders," Hoffman said. "Once the receivers are saying there's a higher chance you're going to get white-listed, the senders are going to say, 'Great, sign me up.'

"As far as we can, tell all the major [e-mail services] are very interested implementing it," he said. "We believe from what they've said that all of them are going to include DKIM fairly high in the list of white-listing technologies."

Microsoft Corp., however, could take longer to adopt it, Hoffman said. "I would put them probably as last, because they are really heavily invested in Sender ID," he said.

Hoffman said that DKIM is not hard to implement and that he would be surprised not to see it in the next versions of major e-mail support applications such as IBM's Lotus Notes and Microsoft's Exchange Server.

Miles Libbey, the antispam product manager for Yahoo Mail and a co-author of DKIM, said Yahoo has been using the original DomainKeys on both its inbound and outbound systems. He said Yahoo plans to switch to the new DKIM specs but is not sure when that will happen.

The IETF publication of the specifications, which will later lead to a formal draft and then eventual final approval, is a first step toward much broader adoption, Libbey said. "By having gone through the IETF process and gaining consensus amongst the entire Internet industry, we've debugged a few issues that surrounded the original implementation of domain key," he said. "Once you actually have it formalized, you're much more confident that the spec is going to be stable."

Eric Allman, the chief science officer at Sendmail, said the DKIM specification and standard will be very important for users. "I do believe this is going to have a major impact initially on phishing," he said.

One benefit is that it will all be handled behind the scenes, as opposed to some current methods that ask users to make decisions on whether to accept or decline incoming messages. "A lot of users can handle that, and a lot of users get confused," he said. "The simplest thing for them to see is that the phisher [messages] just don't show up in their e-mail boxes."

Sendmail is adding DKIM to all of its products, he said.

Once some well-known Web sites such as Yahoo, Paypal and others begin using DKIM, a flood of adoption will occur, he said. "I think that what you're going to see is a rush of places that are going to install it pretty quickly, then it will slow down," Allman said. "The important thing is we'll have a core of sites fairly quickly."

Copyright © 2007 IDG Communications, Inc.

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